This project generated 10 publications (5 in refereed journals and 5 in conference proceedings) during the past year, in addition to 4 papers that have been submitted for publication in refereed journals. We can define four main areas of research progress: (1) modeling methodology for high-order nonlinear physiological systems; (2) modeling of neural systems with long memory and point-process inputs; (3) statistical models of stochastic biological systems; (4) explicit nonstationary models from stimulus-response data. Of particular importance is the general modeling methodology that employs ``principal dynamic modes'' to yield compact high-order nonlinear models within the practical limitations of experimental investigations, solving a long-standing problem of critical importance for physiological system modeling. Pilot applications of this methodology to experimental data from the rat kidney and insect mechanoreceptors have yield new insights into the physiological mechanisms that subserve renal autoregulation and mechano-sensory transduction, respectively.